Comparative Proteomics Analysis of Developing Seed of a Pre-Harvest Seed Deterioration Resistant Soybean Cultivar Under High Temperature and Humidity Stress

The developing seed of soybean is susceptible to high temperature and humidity stress in the field, resulting in pre-harvest seed deterioration. Some soybean cultivars are found to be resistant to the deterioration. However, the resistance mechanism is not yet understood at molecular level. To understand the resistance mechanism, the extracted proteins from the developing seed (R7 period) of a resistant soybean cultivar Xiangdou No. 3 under HTH stress were analyzed by two dimensional electrophoresis (2-DE). The abundance of 45 protein spots were found to be significantly changed, and they were further analyzed by MALDI-TOF MS. Based on the majority of these identified proteins, together with the metabolomics and physiological and biochemical data, a potential resistance mechanism was proposed, which involved in G protein-mediated and calcium-dependent signaling pathways, as well as ROS, NO, ethylene, and auxin signaling pathways; to increase resistance, the stressed developing seed enhanced its cell ultrastructure stability, ROS scavenging, photorespiratory rate, ammonium recycling, protein folding and assembly and secondary metabolite biosynthesis, whereas reduced its energy depletion. In addition, combined with our previous comparative proteomics analysis with a pre-harvest seed deterioration sensitive soybean cv. Ningzhen No. 1, the similarities and differences in the HTH stress-responsive metabolic pathways and cellular processes in the developing seeds between the two soybean cultivars were discussed. Pre-harvest seed deterioration resistant and sensitive soybean cultivars were found to adopt some different metabolic pathways and cellular processes to response to HTH stress. Xiangdou No. 3 possessed more stable cell ultrastructure, lower energy depletion, more enhanced protein folding and assembly and higher protein and oil concentration in its developing seed under HTH stress. All these differences might be the major reasons why Xiangdou No. 3 is more resistant to pre-harvest seed deterioration than Ningzhen No. 1. Such a result allows us to further understand how soybean developing seed responds to HTH stress at protein level and help us in breeding of resistant soybean cultivars.